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Date: Tue, 24 Nov 2015 02:09:36 +0100 From: "Rafael J. Wysocki" <rafael@...nel.org> To: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com>, Alexandra Yates <alexandra.yates@...ux.intel.com> Cc: Len Brown <lenb@...nel.org>, Viresh Kumar <viresh.kumar@...aro.org>, "linux-pm@...r.kernel.org" <linux-pm@...r.kernel.org>, Linux Kernel Mailing List <linux-kernel@...r.kernel.org>, "Rafael J. Wysocki" <rjw@...ysocki.net> Subject: Re: [PATCH V3] SKL intel_pstate update MSR values when changing governors Hi, On Sat, Nov 21, 2015 at 1:16 AM, Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> wrote: > > > On 11/18/2015 02:58 PM, Alexandra Yates wrote: >> >> When changing from powersave to performance governors >> Intel_pstate fails to update the MSR values that reflect the >> max_perf_pct to 100%. For instance in SKL reading rdmsr 0x774: >> >> Governor MSR max_perf_pct >> ========= ======== ============ >> Powersave 80002808 100% >> Powersave 80002008 80% >> Performance 80002028 [error] 100% >> Performance 80002828 [expected] 100% >> >> The line label [error] shows the culprit. At this point the MSR >> should reflect the max_perf_pct that is 100%, that corresponds >> to MSR 80002828 as shown on the next line of the example. Which >> is the maximum performance for the Performance governor. >> Instead it holds back the MSR value previously set by the >> Powersave, in this case 80002028. >> >> This patch allows the system to print the correct MSR value >> 80002828 that corresponds to the 100% max_perf_pct when changing >> from powersave to performance governors. Is this only about what is printed or does it mean that the driver actually uses an incorrect MSR value? >> For more information on the MSR values for SKL please visit >> ISDM under Managing HWP. >> >> Signed-off-by: Alexandra Yates <alexandra.yates@...ux.intel.com> > > Acked-by: Srinivas Pandruvada <srinivas.pandruvada@...ux.intel.com> >> >> --- >> drivers/cpufreq/intel_pstate.c | 2 ++ >> 1 file changed, 2 insertions(+) >> >> diff --git a/drivers/cpufreq/intel_pstate.c >> b/drivers/cpufreq/intel_pstate.c >> index 2e31d09..0eeb7da 100644 >> --- a/drivers/cpufreq/intel_pstate.c >> +++ b/drivers/cpufreq/intel_pstate.c >> @@ -1242,6 +1242,8 @@ static int intel_pstate_set_policy(struct >> cpufreq_policy *policy) >> policy->max >= policy->cpuinfo.max_freq) { >> pr_debug("intel_pstate: set performance\n"); >> limits = &performance_limits; >> + if (hwp_active) >> + intel_pstate_hwp_set(); Honestly, I'm not really sure how this is matching the changelog. What it does is to ensure that the correct limits are used when in the HWP mode too as far as I can say. Is my understanding correct here? >> return 0; >> } >> >> > -- Thanks, Rafael -- To unsubscribe from this list: send the line "unsubscribe linux-kernel" in the body of a message to majordomo@...r.kernel.org More majordomo info at http://vger.kernel.org/majordomo-info.html Please read the FAQ at http://www.tux.org/lkml/
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